1. Field of the Invention
The present invention relates to an image processing apparatus for performing processing of adding a special effect to an image by, for example, processing an original image such as a captured image into a painting-like image and a method of controlling the same.
2. Description of the Related Art
An image sharpening method conventionally extracts edge portions such as contours and borders included in an original image and manipulates them, thereby enhancing the edges of the original image. An image that expresses its contours and borders in this way as linear features can give a strong impression to a viewer.
One of the expressions using this method is a painting-like image that looks like an oil painting, a watercolor painting, a colored pencil drawing, or a pastel drawing. A corona called a halo that appears around an object image is also sometimes preferred as the expression of the painting-like image. Note that the painting-like image in this specification is defined as an image having gradation in a flat portion without contours and borders.
In the related art, however, the edge enhancement is not performed in a flat portion without contours and borders. Since the portion is smooth, and no gradation appears, the image lacks aesthetic appeal. For example, in Japanese Patent Laid-Open No. 5-167852, processing of enhancing contour portions is performed. In this case, no gradation appears in flat portions. To generate a halo, the contrast is enhanced. For example, Japanese Patent Laid-Open No. 2009-17200 discloses adjusting a gamma curve used for gamma correction to improve the contrast on the white side or black side of an image. In the method of Japanese Patent Laid-Open No. 2009-17200, however, since a single gamma curve is applied to the whole processing target image, it is difficult to generate an appropriate halo that makes a processing target image having low contrast look like a painting.